1. Field of the Invention
The present invention relates to a travel route indicating device for use in a vehicle, and more particularly to an improved apparatus for determining and visually indicating a current location, a travelling path and a current travel direction of an automotive vehicle to its driver.
2. Description of the Prior Art
In the attempt to prevent the driver of an automotive vehicle or the like from losing his way when driving such as at night or in unfamiliar surroundings away from his desired route of travel, there have been developed a variety of apparatus which are designed to visually indicate continuously or discretely a due current position or the like information on the vehicle by way of an indication panel or display screen including a related road map or the like disposed at the driver's seat so that he may be provided with necessary ready guidance relating to the vehicle's current status of travelling with respect to a desired course of travel.
In the conventional travel route indicating apparatus for such an application, a current travel distance of a vehicle is detected in accordance with its travel speed and time by using a distance detecting section, a current bearing and a current quantity of azimuthal deviation of the vehicle are detected by a bearing detecting section which employs a rate gyroscope or the like adapted to detect a possible angular velocity produced about the axis of yawing motion of the vehicle, a current location of the vehicle along its travel route is obtained from an arithmetic operation on the thus-obtained data, and the results of this arithmetic operation are stored in sequence, and indicated visually by way of spot information varying from time to time on a display screen upon which there is presented a transparent road map of routes or roads along which the vehicle travel.
With the conventional construction as described above, however, it is generally arranged in practice that the power supply to such travel route indicating apparatus is interlocked with the opening and closing operation of the ignition key switch of the vehicle. In this connection, therefore, there may be frequent possibilities of shut-offs of the power supply to the apparatus such as when stopping the engine of the vehicle for gas or for a meal when travelling. Thus the data on the travel of the vehicle up to that point of stopping is missed due to the volatility of the memory of the apparatus.
The present invention is essentially directed toward overcoming such inconveniences as experienced in the conventional travel route indicating apparatus.